input=
<articles>
    <article name="chair" onStock="50">
        <prize>10.0</prize>
        <quantity>100</quantity>
    </article>
    <article name="table" onStock="30">
        <prize>20.0</prize>
        <quantity>200</quantity>
    </article>
</articles>

Q0: identity transform: update(//node() | //@*, .)
output=
<articles>
    <article name="chair" onStock="50">
        <prize>10.0</prize>
        <quantity>100</quantity>
    </article>
    <article name="table" onStock="30">
        <prize>20.0</prize>
        <quantity>200</quantity>
    </article>
</articles>

Q1: delete all attributes: update(//@*, ())
output=
<articles>
    <article>
        <prize>10.0</prize>
        <quantity>100</quantity>
    </article>
    <article>
        <prize>20.0</prize>
        <quantity>200</quantity>
    </article>
</articles>

Q2: delete all chairs: update(//article[@name='chair'], ())
output=
<articles> 
    <article name="table" onStock="30">
        <prize>20.0</prize>
        <quantity>200</quantity>
    </article>
</articles>

Q3: delete all chairs (equivalent): update(//article, if (@name='chair') then () else .)
output=
<articles> 
    <article name="table" onStock="30">
        <prize>20.0</prize>
        <quantity>200</quantity>
    </article>
</articles>

Q4: delete stock info of chairs: update(//article/@onStock[../@name='chair'], ())
output=
<articles>
    <article name="chair">
        <prize>10.0</prize>
        <quantity>100</quantity>
    </article>
    <article name="table" onStock="30">
        <prize>20.0</prize>
        <quantity>200</quantity>
    </article>
</articles>

Q5: set prize of chair to 9.5: update(//article[@name='chair']/prize, 9.5)
output=
<articles>
    <article name="chair" onStock="50">
        <prize>9.5</prize>
        <quantity>100</quantity>
    </article>
    <article name="table" onStock="30">
        <prize>20.0</prize>
        <quantity>200</quantity>
    </article>
</articles>

Q6: set attribute value to 0: update(//article[@name='chair']/@onStock, 0)
output=
<articles>
    <article name="chair" onStock="0">
        <prize>10.0</prize>
        <quantity>100</quantity>
    </article>
    <article name="table" onStock="30">
        <prize>20.0</prize>
        <quantity>200</quantity>
    </article>
</articles>

Q7: increment attribute value by 50: update(//article[@name='chair']/@onStock, . + 50)
output=
<articles>
    <article name="chair" onStock="100">
        <prize>10.0</prize>
        <quantity>100</quantity>
    </article>
    <article name="table" onStock="30">
        <prize>20.0</prize>
        <quantity>200</quantity>
    </article>
</articles>

Q8: make all articles a bit cheaper: update(//article/prize, . * 0.95)
output=
<articles>
    <article name="chair" onStock="50">
        <prize>9.5</prize>
        <quantity>100</quantity>
    </article>
    <article name="table" onStock="30">
        <prize>19</prize>
        <quantity>200</quantity>
    </article>
</articles>

Q9: move article position: move second article before first article: update(//article[1], (//article[2], .))
output=
<articles>
    <article name="table" onStock="30">
        <prize>20.0</prize>
        <quantity>200</quantity>
    </article>
    <article name="chair" onStock="50">
        <prize>10.0</prize>
        <quantity>100</quantity>
    </article> 
</articles>

Q10: append some new elements at end: update(/articles/article[last()], (., <foo/>, <article name='sofa' onStock='40'> <prize>30.0</prize> <quantity>500</quantity> </article>))
output=
<articles>
    <article name="chair" onStock="50">
        <prize>10.0</prize>
        <quantity>100</quantity>
    </article>
    <article name="table" onStock="30">
        <prize>20.0</prize>
        <quantity>200</quantity>
    </article>
    <foo/>
    <article onStock="40" name="sofa">
        <prize>30.0</prize>
        <quantity>500</quantity>
    </article>
</articles>

Q11: rename an attribute: update(//@onStock, attribute {'availability'} { string(.) })
output=
<articles>
    <article name="chair" availability="50">
        <prize>10.0</prize>
        <quantity>100</quantity>
    </article>
    <article name="table" availability="30">
        <prize>20.0</prize>
        <quantity>200</quantity>
    </article>
</articles>

Q12: rename an element: update(//article/prize, <price>{string(.)}</price>)
output=
<articles>
    <article name="chair" onStock="50">
        <price>10.0</price>
        <quantity>100</quantity>
    </article>
    <article name="table" onStock="30">
        <price>20.0</price>
        <quantity>200</quantity>
    </article>
</articles>

Q13: turn an element into an attribute: update(//article/prize, attribute {'price'} {string(.)})
output=
<articles>
    <article name="chair" onStock="50" price="10.0"> 
        <quantity>100</quantity>
    </article>
    <article name="table" onStock="30" price="20.0"> 
        <quantity>200</quantity>
    </article>
</articles>

Q14: add comments before and after root element: update(/*, (comment {'database of articles on stock'}, ., comment {'end of database'} ))
output=
<!--database of articles on stock-->
<articles>
    <article name="chair" onStock="50">
        <prize>10.0</prize>
        <quantity>100</quantity>
    </article>
    <article name="table" onStock="30">
        <prize>20.0</prize>
        <quantity>200</quantity>
    </article>
</articles><!--end of database-->

Q15: delete all articles, only retaining their prize: update(//article, prize)
output=
<articles>
    <prize>10.0</prize>
    <prize>20.0</prize>
</articles>

Q16: wrap each article into a new element with a derived attribute: update(//article, <envelope total='{prize * quantity}'>{.}</envelope>)
output=
<articles>
    <envelope total="1000">
        <article name="chair" onStock="50">
            <prize>10.0</prize>
            <quantity>100</quantity>
        </article>
    </envelope>
    <envelope total="4000">
        <article name="table" onStock="30">
            <prize>20.0</prize>
            <quantity>200</quantity>
        </article>
    </envelope>
</articles>

Q17: add a summary element to each article: update(//article/*[1], (<summary total='{../prize * ../quantity}'></summary>, .))
output=
<articles>
    <article name="chair" onStock="50">
        <summary total="1000"/>
        <prize>10.0</prize>
        <quantity>100</quantity>
    </article>
    <article name="table" onStock="30">
        <summary total="4000"/>
        <prize>20.0</prize>
        <quantity>200</quantity>
    </article>
</articles>

Q18: add item number ID comment before each article: update(//article, (comment {index-of(../*, .)}, .))
output=
<articles>
    <!--1-->
    <article name="chair" onStock="50">
        <prize>10.0</prize>
        <quantity>100</quantity>
    </article>
    <!--2-->
    <article name="table" onStock="30">
        <prize>20.0</prize>
        <quantity>200</quantity>
    </article>
</articles>

Q19: add item number ID attribute to each article: update(//article/*[1], (., attribute {'id'} {index-of(../../*, ..)} ))
output=
<articles>
    <article name="chair" onStock="50" id="1">
        <prize>10.0</prize>
        <quantity>100</quantity>
    </article>
    <article name="table" onStock="30" id="2">
        <prize>20.0</prize>
        <quantity>200</quantity>
    </article>
</articles>